Japanese clock (wadokei)

Until 1873 Japan kept hours that stretched in summer and shrank in winter, and for more than 200 years its clockmakers built ingenious machines to follow them.

What is a wadokei?

Wadokei is the Japanese term for the traditional mechanical clocks made in Japan before the country switched to Western timekeeping. Their purpose was unusual: rather than counting 24 equal hours, they kept a seasonal, or temporal, hour system in which the hours themselves changed length through the year.

According to the Seiko Museum in Tokyo, these clocks were made and used for more than 200 years, in forms that included lantern clocks, pillar clocks and small pillbox-shaped pocket watches. Many were richly finished, with engraved brass, lacquer or tortoiseshell cases.

How temporal hours worked

Under the old system, daytime and nighttime were each divided into six equal parts called toki, with sunrise and sunset as the boundaries. A daytime hour was long in summer and short in winter, and the night hours did the opposite. The Science Museum Group notes that, because daylight changes through the year, these hours were rarely equal in length.

Each of the 12 toki was named after an animal of the zodiac, starting with the Rat at midnight. A second count numbered them backward from nine: midnight and midday were both 9, followed by 8, 7, 6, 5 and 4 before the count started again. People added words such as dawn, dusk, day or night to make clear which 6 or 9 they meant.

The system was old by the time clocks arrived. The Japan Clock and Watch Association says temporal hours were in use from the Kamakura and Muromachi periods (1185-1573), while fixed hours had been used in part much earlier and were used alongside the temporal system during the Edo period. So a wadokei was not inventing a new way of telling time; it was mechanizing one that people already lived by.

See also: how long daylight lasts where you are today on OnlineClock.app.

How the clocks kept up

The European clocks that reached Japan in the 16th century were designed for equal hours, so Japanese makers adapted them. On a single foliot clock, the horizontal bar that regulates the speed carries small weights; moving them in or out changes the rate. Because day hours and night hours differed, the weights had to be moved twice a day, at dawn and at dusk.

The double foliot balance, developed at the end of the 17th century, solved this with two foliots, one set for daytime and one for night, that swapped over automatically. The weights then needed adjusting only 24 times a year, once for each of the traditional solar terms. Toward the end of the Edo period, makers turned to pendulums or hairsprings, which were more accurate but hard to vary, so they moved the hour markers instead, for example on a dial of hour plates that slid along a rail as the seasons changed.

From Western gift to Japanese craft

The earliest recorded mechanical clock in Japan was a self-striking clock given by the missionary Francis Xavier, who arrived in 1551, to Ouchi Yoshitaka, lord of Suo; it has not survived. The oldest clock still in Japan is a spring-driven table clock presented to Tokugawa Ieyasu, founder of the Edo shogunate, in 1612 by the governor of Spanish Mexico. It is kept as a treasure at Kunozan Toshogu shrine in Shizuoka.

Missionary schools in Kyushu and Kyoto taught clockmaking alongside printing, organ music and the making of astronomical instruments, and smiths trained there began building Japan's own clocks. The Seiko Museum reports that Sukezaemon Tsuda the first was Japan's first maker of a mechanical clock; a double foliot lantern clock with an alarm, dated 1688 and attributed to the third Sukezaemon Tsuda, is the oldest known example with a double foliot.

Types and how to recognize them

Lantern clocks were the classic early form, weight-driven with a bell for striking, and the Seiko Museum's lantern clocks include both single and double foliot types. Pillar clocks are long, narrow clocks that hang on a house post: a weight falls inside the trunk, and a pointer on the weight moves past a column of hour plates that can be slid into new positions as the seasons change. The Science Museum's 19th-century pillar clock works exactly this way, with a verge and foliot escapement.

Other forms include spring-driven table clocks, small pocket watches and rare wall clocks whose hands lengthen and shorten through the year. A clue on almost any wadokei is the dial: instead of the numbers 1 to 12, it carries zodiac characters or the numbers 9 down to 4, often on a rotating dial or movable plates.

Individual pieces show how inventive the makers were. The Seiko Museum's collection includes a lantern clock 218 cm tall said to have come from the tower of the old Inuyama Castle, its dial inscribed as repaired in November 1799; a 136.5 cm pillar clock made by Yamato Araki between 1772 and 1780; and a paperweight clock of around 1818-1829 by Ohno Yasaburo, a clockmaker at the shogunate's calendar office. Its late Edo wall clock with a circle-graph dial has hands that lengthen toward the summer solstice and shorten toward the winter solstice.

Smaller pieces could be just as clever. The museum's turtle-shell pocket watch hides a sundial and a compass in its lid, and a note kept with it suggests it may have belonged to Tokugawa Nariaki, lord of Mito.

When the hours became equal

The end came with the calendar reform. The Japan Clock and Watch Association explains that when Japan switched from its lunisolar calendar to the solar calendar, the day that would have been December 3, 1872 became January 1, 1873, and the fixed-hour system used today was prescribed as part of the same change. The traditional clocks then gradually went out of use.

See also: how the equal hour we use today is defined on OnlineClock.app.

Keep exploring

Sources

1. What is a Traditional Japanese Clock (Wadokei)? (Seiko Museum Ginza)
2. Seasonal Time System (Seiko Museum Ginza)
3. Major Types of Traditional Japanese Clocks (Seiko Museum Ginza)
4. Japanese wadokei pillar clock (Science Museum Group)
5. The time system of Japan (Japan Clock and Watch Association)